Oil Tech: Functions

Posted in Blog by admin with 2 Comments

Jun2012 09



In previous articles in the Oil Tech Information Series focused on the physical and chemical properties of engine oil, as well as some of the conditions that cause oil to break down, become acidic, and form sludge. While all of this is good knowledge, it is also important to understand all of the ways the oil in your engine functions to ensure proper lubrication, minimize wear, and keep your engine running smoothly.

The most important function of the engine oil is to provide lubrication. Basically, there are two different ways this happens: by creating a pressurized film within bearing journals and by creating an oil film between non pressurized surfaces.

Pressurized bearings rely on oil pressure to create a thin film between two surfaces. This type of bearing is found on rotating parts in the block and cylinder head, such as the crankshaft main bearings, rod bearings, and camshaft journals/bearings. The oil pump lubricates these bearings by sending pressurized oil through the galleries, which is then pumped into the bearing through holes in the main crankshaft journals or camshaft journals. The rod bearings are lubricated through channels through the crankshaft, which transfers the pressurized oil from the main bearings journals to the rod bearing journals. In some cases, the piston wrist pin also receives pressurized oil through rifle-drilled channels that run through the connecting rod. In other cases, the wrist pin receives oil through splash oiling through holes in the wrist pin end of the connecting rod. Pressurized bearings rely on the viscous properties of the oil to create film strength, which allows the inner bearing to float inside the outer bearing.

The oil also lubricates non-pressurized surfaces in the engine, such as the contact patch between the cam lobe and the cam follower or the piston ring and cylinder wall. Since the contact surfaces are in contact with each other, lubrication becomes very important. Additionally, wear becomes an issue, and this is the main reason for anti-wear additives and extreme pressure additives such as zinc, phosphorus, and molybdenum (more on this in a later article).

Where the piston ring is constantly sliding up and down, the cylinder cross hatching plays an important role in maintaining an oil film by creating tiny crevices to hold the oil. Oil on the cylinder wall/piston ring contact surface is also important for creating a strong seal to hold the engine compression within the combustion chamber.

While lubrication of moving parts is the most important function of the oil within the engine, your oil also performs other vital functions by providing corrosion and oxidation resistance for metal parts, cooling engine parts and transferring heat away from the pistons, sometimes by using oil squirters that spray the bottom of the piston. The oil additive package will also contain detergents to help keep the engine clean and minimize sludge and varnish and seal conditioners, as most seals would deteriorate at the temperature the engine operates without them.

Overall, the oil truly is the lifeblood of the engine, performing many vital functions to keep the engine operating smoothly and cleanly for years.

For the complete series of Oil Tech posts, check out this link

Post dicussion

2 Responses to “Oil Tech: Functions”

  • Lacy July 19, 2012

    In internal combustion engines , the gudgeon pin (UK, wrist pin US) is that which connects the piston to the connecting rod and provides a bearing for the connecting rod to pivot upon as the piston moves.

  • Lavern July 24, 2012

    The severity of the noise depends on how badly the bearings are worn. The noise can range from a light tap to a heavy knock or even a pounding, when the bearing becomes extremely damaged or spun. When the noise is at this level, removing the engines oil pan may expose the problem.

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